Being a Betaphile, I remember the envy of seeing linear stereo sound on VHS tapes, then breathing a huge sigh of relief and a hearty laugh when Beta Hi-Fi debuted, completely blowing away VHS stereo. Of course, the VHS camp countered with VHS Hi-Fi, but at least Beta was first!

In the original VHS specification, audio was recorded as baseband in a single linear track, at the upper edge of the tape, similar to how an audio compact cassette operates. The recorded frequency range was dependent on the linear tape speed. For the VHS SP mode, which already uses a lower tape speed than the compact cassette, this resulted in a mediocre frequency response of roughly 100 Hz to 10 kHz for NTSC;[citation needed] frequency response for PAL VHS with its lower standard tape speed was somewhat worse. The signal-to-noise ratio (SNR) was an acceptable 42 dB. Both parameters degraded significantly with VHS's longer play modes, with EP/NTSC frequency response peaking at 4 kHz.

Audio cannot be recorded on a VHS tape without recording a video signal, even in the audio dubbing mode. If there is no video signal to the VCR input, most VCRs will record black video as well as generate a control track while the audio is being recorded. Some early VCRs would record audio without a control track signal, but this was of little practical use since the absence of a control track signal meant that the linear tape speed was irregular during playback.

More expensive decks offered stereo audio recording and playback. Linear stereo, as it was called, fit two independent channels in the same space as the original mono audiotrack. While this approach preserved acceptable backward compatibility with monoaural audio heads, the splitting of the audio track degraded the signal's SNR to the point that audible tape hiss was objectionable at normal listening volume. To counteract tape hiss, decks applied Dolby B noise reduction for recording and playback. Dolby B dynamically boosts the mid-frequency band of the audio program on the recorded medium, improving its signal strength relative to the tape's background noise floor, then attenuates the mid-band during playback. Dolby B is not a transparent process, and Dolby-encoded program material will exhibit an unnatural mid-range emphasis when played on non-Dolby capable VCRs.

High-end consumer recorders took advantage of the linear nature of the audio track, as the audio track could be erased and recorded without disturbing the video portion of the recorded signal. Hence, "audio dubbing" and "video dubbing", where either the audio or video are re-recorded on tape (without disturbing the other), were supported features on prosumer linear video editing-decks. Without dubbing capability, an audio or video edit could not be done in-place on master cassette, and requires the editing output be captured to another tape, incurring generational loss.

Studio film releases began to emerge with linear stereo audiotracks in 1982. From that point onward nearly every home video release by Hollywood featured a Dolby-encoded linear stereo audiotrack. However, linear stereo was never popular with equipment makers or consumers."

The first is a pair of linear audio tracks along the edge of the tape. A mono deck will combine both tracks by reading them with the same head.
The second is a series of helically-scanned tracks picked up by AFM heads on the video drum.
The third is the same as the first with Dolby noise reduction.

The linear track can be mono or stereo. The linear track is recorded linearly (just like a cassette) along the side of the tape. It has a low bandwidth, especially with slower tape speeds. The Hi-Fi track is recorded by the helical scan heads, next to the video tracks. This page has a picture:

A is the linear track(s), D is the hi-fi track. All tapes must include a linear track, and all players must be able to play the linear track. If the linear track is stereo it can be encoded with Dobly Pro Logic surround sound.

There should be 100 percent crosstalk when playing a stereo linear track with a mono player. Ie, it should be a 50:50 mix. The problem would be when the playback head is mis-aligned and you get an uneven mix.

I believe this picture is not entirely correct - HiFi track may use different angle (so audio track will be not parallel to video) and it use different spectrum (thus provide frequency separation) - VCR record B/W signal (except linear audio) - all signals (except linear audio) are converted to FM but they are located in non overlapping (from spectrum perspective) zones - HiFi audio occupy spectrum before chrominance and chrominance before luminance - as HiFi FM has lowest frequency thus it can penetrate tape deeper than for example chrominance and especially luminance signals.

In VHS Hi-Fi, FM audio is placed between chrominance and luminance bands. Audio tracks are perfectly parallel to video tracks; they have to be, since the heads are on the same circle. Audio tracks are recorded deeper into the oxide and video tracks are recorded on top of them. The "different angle" is head azimuth, which makes the appropriate signal stronger for the appropriate playback head. FM capture effect does the rest.

In VHS Hi-Fi, FM audio is placed between chrominance and luminance bands. Audio tracks are perfectly parallel to video tracks; they have to be, since the heads are on the same circle. Audio tracks are recorded deeper into the oxide and video tracks are recorded on top of them. The "different angle" is head azimuth, which makes the appropriate signal stronger for the appropriate playback head. FM capture effect does the rest.

All "linear" means as far as VHS goes is that it's not VHS HiFi, which is helically recorded like the video and actually was quite good except the mfr's usually put non defeatable peak limiters in. Linear just means standard AM radio quality audio and I suspect it's another one of those stupid marketing names.

No, jagabo was correct: the non-hifi audio head(s) are stationary (not rotating - the video & hifi heads do that), so when the tape passes by LINEARLY, it gets recorded, linearly, along the top edge. (Bottom edge has control track).

As far as I know VCR's capable of recording and reading Linear Stereo disappeared quickly after the introduction of HiFi Stereo, Chances of finding a VCR that is capable of Linear Stereo are slim and finding a pre recorded tape with such audio track is even slimmer. All VCR's are capable of reading and recording a mono linear audio track along the edge of the tape.